(1) Summary of the Invention
The present invention relates to novel composite materials and methods for the preparation thereof. In particular the present invention relates to composite material prepared by a method which uses combinations of relatively large glass microspheres and relatively small polymer microspheres admixed with a solid polymer, wood flour (particles) and natural fibers to provide composite materials having unique physical properties.
(2) Description of Related Art
Syntactic foam materials are mixtures of polymers and hollow microspheres. The resulting composite materials are lighter in weight than the solid polymer.
The patent art is shown by U.S. Pat. No. 3,900,543 to Davis; U.S. Pat. No. 3,902,937 to Arndt et al; U.S. Pat. No. 4,250,136 to Rex; U.S. Pat. No. 4,403,107 to Hoffman; U.S. Pat. No. 4,788,230 to Mudge; U.S. Pat. No. 4,447,565 to Lula et al; U.S. Pat. No. 5,242,637 to Inoue et al; U.S. Pat. No. 4,919,866 to Kubbutat; U.S. Pat. No. 5,132,061 to Lindeman et al; U.S. Pat. No. 5,492,756 to Seale et al; and U.S. Pat. No. 5,585,054 to Evans.
Davis et al describe buoyant foams using glass or plastic beads. Arndt et al describe a foam containing glass microspheres. Rex describes composite materials made of microspheres (10 to 200 microns) and macrospheres (500 to 15,000 microns) with a polymer as a foam core. Hoffman describes a polymer material containing hollow glass microspheres. Mudge describes syntactic foams prepared by mixing a polymer and microspheres. Lula et al describe microspheres used with a molecular sieve for water absorption. Inoue et al describe composite products with a syntactic foam core. Kubbutat describes a foam containing glass microspheres and an epoxy resin and glass fibers. Lindeman et al describe gaskets made of polymer microspheres. The microspheres are expanded in the formation of the gasket.
The use of kenaf fibers in composite materials is described in U.S. Pat. No. 5,585,054 to Evans and U.S. Pat. No. 5,492,756 to Seale et al. These patents do not describe the use of microspheres.
The problem the prior art is faced with is to provide very low cost, higher strength composite materials using microspheres and various natural fibers, particularly kenaf fibers.